The present disclosure relates to level shifting circuits and methods
Unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In many electronic systems, different circuits are powered by different power supply voltages. When signals are communicated between different circuits powered by different power supply voltages, the signals are typically level shifted to be operable under new power supply voltage conditions.
FIG. 1 illustrates prior art level shifting. In circuit 100, circuitry 101 is connected to power supply voltage Vdd1 and ground. Similarly, circuitry 102 is connected to power supply voltage Vdd2 and ground. In this example, Vdd2 is greater than Vdd1. Circuit 100 includes a level shift circuit 103 for modifying signals that are transmitted from circuitry 101 to circuitry 102 across a power supply boundary 104. Power supply boundary 104 distinguishes between signal levels in circuitry 101 and circuitry 102, which are powered by different power supply voltages.
As illustrated in FIG. 1, a signal 110 may have a low level of zero volts (i.e., ground) and a high level of Vdd1. Level shift circuit 103 may produce a modified signal 111 having a low level of zero volts and a high level of Vdd2. Thus, signal 110 and modified signal 111 have the same low level of zero volts. One example of a level shift operation is translating a 0-1.8 v signal used in one part of a system to a 0-3.3 v signal used in another part of the system.